The objectives of the proposed project are 1) to quantitate the dynamics of antibody function by measuring the segmental flexibility of several classes of immunoglobulins and the mobility of immunoglobulin receptors on B cells in the nanosecond and microsecond time range; and 2) to elucidate the tertiary structure of antibody combining sites and the contributions of the heavy and light chains. Theses problems will be investigated by using fluorescence and circular dichroism techniques. Flexibility and mobility will be determined from rotational relaxation times obtained by nanosecond fluorescence depolarization measurement. Tertiary structure of combining sites will be determined from the induced circular dichroism of bound hapten. These techniques have been previously utilized in our laboratory and shown to be feasible. BIBLIOGRAPHIC REFERENCES: Lovejoy, C., Holowka, D.A. and Cathou, R.E., Nanosecond Fluorometry of Anti-pyrene Antibody, Federation Proceedings 34, 544A (1975). Gollogly, J.R. and Cathou, R.E. Sequential Appearance of Three Different Anti-Fluorescein Combining Sites in Hyperimmunized Rabbits. Characterization by Circular Dichroism and Binding Studies, Journal of Immunology, 113, 1457 (1974).